Abstract

The invention relates to a method for the surface treatment of a part made of aluminum, magnesium, or one of the alloys thereof, with a view to protecting said part from corrosion, said method including consecutively immersing the part in a fist aqueous bath containing a corrosion-inhibiting metal salt and an oxidizing compound, and a second aqueous bath containing an oxidizing compound and a corrosion-inhibiting rare-earth salt. Said method can be carried out for the chemical conversion of aluminum or the alloys thereof, and of magnesium or the alloys thereof, on parts that have not been previously treated, or after a step of anodizing the part, in order to seal the anodic layer.

IPC Classes  ?

• C23C 22/34 - Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH < 6 containing fluorides or complex fluorides
• C23C 22/83 - Chemical after-treatment
• C25D 11/24 - Chemical after-treatment

Abstract

The invention relates to a method for anodizing a part made of aluminum or of an aluminum alloy, by immersing the part in an aqueous bath essentially comprising sulfuric acid at a concentration of 150 to 250 g/L and at a temperature of 5 to 25°C, then applying, to the part, a DC voltage according to a voltage profile comprising a voltage increase at a rate of 1 to 32 V/min, and then maintaining the voltage at a so-called plateau voltage value of 12 to 20 V for a duration sufficient for obtaining, at the surface of the part, an anode layer having a thickness of 3 to 7 µm and/or a layer weight of 20 to 150 mg/dm2.

IPC Classes  ?

• C25D 11/08 - Anodisation of aluminium or alloys based thereon characterised by the electrolytes used containing inorganic acids
• C25D 11/02 - Anodisation
• C25D 11/16 - Pretreatment
• C25D 11/24 - Chemical after-treatment
• C25D 11/38 - Chromatising